1. Field of the Invention
The present invention relates to a solenoid valve for discharging a reaction gas from fuel cells of a fuel cell system.
2. Description of the Related Art
Heretofore, solid polymer membrane fuel cell devices have a stack of cells (hereinafter referred to as a fuel cell stack) each comprising an anode, a cathode, and a solid polymer electrolyte membrane interposed between the anode and the cathode. When hydrogen is supplied as a fuel to the anode and air is supplied as an oxidizing agent to the cathode. Hydrogen ions are generated at the anode by a catalytic reaction, and move through the solid polymer electrolyte membrane to the cathode. Electric power is generated in the fuel cell stack by the electrochemical reaction.
The fuel cell devices are combined with an air compressor for supplying air as a reactant gas to the cathodes and a pressure control valve for supplying hydrogen as a reactant gas to the anodes. The pressure of the reactant gas supplied to the anodes with respect to the pressure of the reactant gas supplied to the cathodes is adjusted to a predetermined pressure for thereby achieving a predetermined power generation efficiency, and the flow rate of the reactant gas supplied to the fuel cell stack are controlled to obtain a desired fuel cell output.
The applicant of the present application has proposed a solenoid valve which can stably and smoothly be opened and closed at low temperatures for appropriately discharging a reactant gas from fuel cell devices (Japanese patent application No. 2002-347156).
One known prior invention relevant to the present invention is concerned with a fuel cell system having a check valve that is inserted in a hydrogen return line thereof and selectively openable and closable by a controller for preventing excessive hydrogen from being recirculated and also preventing fresh hydrogen from being discharged out of the fuel cell system while hydrogen is being purged, thereby to reliably purge hydrogen and prevent fresh hydrogen from being wasted (see, for example, Japanese laid-open patent publication No. 2002-93438).